The present invention is directed at a lube oil having satisfactory anti-wear and friction reducing properties while having a reduced phosphorus content. More specifically, the present invention is directed at a lube oil comprising a basestock, a metal dialkyldithiophosphate, and an aryl carbonate ester.
Typically, in present-day lube oil formulations for internal combustion engines, phosphorus-containing compounds, such as zinc dialkyldithiophosphate (ZDDP), are added to the lube oil formulation to provide improved anti-wear properties. However, it has been found that phosphorus from phosphorus-containing compounds becomes deposited on the catalyst in catalytic converters, thereby decreasing the efficiency of catalytic converters over time. At the present time automotive lube oils typically contain a maximum of about 0.10 to about 0.14 wt. % phosphorus. To reduce the rate at which catalytic converters become fouled by phosphorus, it has been suggested that the maximum phosphorus content of lube oils be reduced to a range of about 0.05 to about 0.08 wt. %.
The use of carbonates in lube oils is known. U.S. Pat. Nos. 2,340,331 and 2,387,999 disclose the use of diethyl, diamyl, dilauryl, diphenyl, dicresyl, di-o-cresyl, dibenzyl, mono-ethyl, and mono-phenyl carbonates in lube oils to increase the extreme pressure characteristics and reduce the rate of wear of lubricating oils.
European Patent Publication No. 89,709 discloses the use of organic carbonic esters of higher alcohols in lubricants for internal combustion engines. Wear and Coefficient of Friction test data are reported.
It is desirable to decrease the concentration of phosphate-containing compounds, such as zinc dialkyldithiophosphate, present in lubricating oil to thereby decrease the rate at which phosphates become deposited on the catalyst.
It also is desirable to provide lube oils having anti-wear properties comparable to presently available lube oils, while also having a reduced phosphorus content.
It also is desirable to provide a lube oil having Coefficients of Friction comparable to presently available lube oils, while having a reduced phosphorus content.
The present invention is directed at a lube oil and method of manufacturing same wherein the lube oil comprises:
A. a basestock;
B. diphenyl carbonate; and,
C. a metal phosphate salt.